TW202323574A - Processes for forming metal oxide thin films on electrode for interphase control - Google Patents

Abstract

This invention provides a novel solution to form an artificial interphase on the electrode to protect it from fast declining electrochemical behaviors, by depositing Metal Oxides Layer, by ALD or CVD. Metals discussed here are IVA-VIA elements (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W). The film needs to be thin, possibly discontinuous, and lithium ion conductive enough, so that the addition of this thin film interface allows fast lithium ion transfer at the interface between electrode and electrolyte.

Description

Method for forming metal oxide thin film for interface control on electrode

The present invention relates to a method of coating a cathode or cathode active material with a metal oxide film.

During the first few cycles of a Li-ion battery, the formation of a solid electrolyte interface (SEI) on the anode and/or cathode by the decomposition of the electrolyte at the electrolyte/electrode interface was observed. The initial capacity loss of Li-ion cells is due to the depletion of lithium during the formation of this SEI. Moreover, the formed SEI layer is inhomogeneous and unstable, which cannot effectively passivate the electrode surface to prevent the degradation of electrode active materials due to the continuous decomposition of the electrolyte. The SEI layer may physically crack during battery cycling, and lithium dendrites may appear and cause short circuits, which in turn lead to thermal runaway. In addition, the SEI layer also creates a potential barrier that makes the intercalation of lithium ions in the electrode more difficult.

In the current design, Li-ion cells have (lithium) metal oxides at the surface of the electrodes and/or electrode active materials by wet-coating, dry-coating, or sputtering continuous films of metal oxides or/and phosphates , phosphate or fluoride coating (for example, Al _x O _y , Li _{x My} PO _z , M = Nb, Zr, Al, Ti, etc., or AlM _x F _y , M = W, Y, etc.) to stabilize the electrode interface with the electrolyte. Lithium-containing thin films are well known for their use as surface coatings for electrode materials in Li-ion battery applications. Examples of lithium-containing thin films include LiPON, lithium phosphate, lithium borate, lithium borophosphate, lithium niobate, lithium titanate, lithium zirconium oxide, and the like. Surface coating of electrodes by ALD/CVD technique is a better means to form the expected solid electrolyte interface film, thus avoiding the formation of these unstable layers. However, vapor deposition of lithium-containing films is difficult due to the lack of suitable lithium precursors for high-volume manufacturing: most lithium precursors are not volatile or stable enough, and they may contain undesired impurities. Another important application of interfacial films is to form solid electrolyte materials used in solid-state batteries. Solid-state batteries are solvent-free systems that offer longer life, faster charge times, and higher energy densities than conventional lithium-ion batteries. Solid-state batteries are considered the next technological stage in battery development. With ALD/CVD technology, uniform and conformal electrode/electrolyte interface films can be obtained even on complex structures like 3D batteries.

Silicon anodes are also within the application range of interfacial films. Silicon is considered to be the next-generation anode in the development of Li-ion batteries. At the same potential level (0.2 V vs. Li ^{+ /} Li) as the graphite anode (0.05 V vs. mAh g ^-1 ) provides a higher specific capacity (3600 mAh g ^-1 ). The main disadvantage of silicon anodes is volume expansion of up to 300% during charge/discharge, leading to SEI instability and physical cracks in the electrode.

The application of interfacial films can be extended to lithium metal anode technology. Lithium metal anodes are considered as lithium-ion batteries (LIBs) because they can deliver at least 3 times the theoretical capacity compared to LIBs. Lithium metal has also attracted attention due to its high capacity (10 times that of graphite), reduced battery size and simple manufacturing process. However, an uncontrolled Li metal surface may lead to the growth of Li dendrites, causing short circuits and eventually fires.

For next-generation cathode active materials, much research has focused on identifying and developing metal oxide cathode materials. Among the wide range of layered oxides, Ni-rich cathode materials like NMC (lithium nickel manganese cobalt oxide) and NCA (lithium nickel cobalt aluminum oxide) are currently the most promising candidates for practical applications. However, Ni-rich cathode materials tend to become amorphous when a high voltage is applied. One of the major disadvantages of these metal oxide materials is the continuous dissolution of transition metals, especially nickel, due to the parasitic reaction of the cathode material with the electrolyte. This leads to structural degradation of the cathode active material, with gas (O ₂ ) release at the electrode/electrolyte interface during battery charging. Furthermore, dissolved nickel ions move to the anode side, and their deposition on the anode surface triggers rapid decomposition of the SEI at the anode, eventually leading to battery failure.

Spinel cathode materials have been extensively studied due to their high rate capability and low or zero cobalt content. One of the main problems with spinel cathode materials like LMO (Lithium Manganese Oxide), LNMO (Lithium Nickel Manganese Oxide) is manganese divalent ions (2 Mn ³⁺ → Mn ⁴⁺ + Mn ²⁺ ) during battery charging The dissolution of Ni, which mainly occurs at the electrode/electrolyte interface, is then redeposited on the anode side and destroys the SEI of the anode by the same mechanism as that of Ni-rich cathode materials.

x

3（LTO）、石墨、矽、含矽合金、含錫合金、及其組合。 To address interface issues between the electrolyte and the cathode electrode, such as transition metal dissolution, excessive decomposition of the electrolyte, thin film deposition can be applied on the cathode and/or cathode material. For example, US 8535832 B2 disclosed that metal oxides (Al ₂ O ₃ , Bi ₂ O ₃ , B 2 O ₃ , ZrO ₂ , MgO, _{Cr 2 O 3} , MgAl ₂ O ₄ , Ga ₂ O ₃ , SiO ₂ , SnO ₂ , CaO, SrO, BaO, TiO ₂ , Fe ₂ O ₃ , MoO ₃ , MoO ₂ , CeO ₂ , La ₂ O ₃ , ZnO, LiAlO ₂ or combinations thereof) wet-coated to a cathode containing Ni, Mn, and Co on the active material. US 9543581 B2 describes the dry coating of amorphous _Al2O3 onto precursor _particles of cathode active material comprising the elements Ni, Mn and Co. US 9614224 B2 describes Li _x PO _y Mn _z coatings on cathode active materials comprising Mn using the sputtering method. US 9837665 B2 describes thin film coatings of lithium phosphorus oxynitride (LiPON) using sputtering on cathode active materials comprising: Li, Mn, Ni and An oxygen-containing compound of at least one of the dopants. US 9196901 B2 describes _Al2O3 thin film coatings using atomic layer deposition (ALD) on cathode laminates and cathode active materials comprising Co, Mn, V, Fe, Si or _Sn and Is an oxide, phosphate, silicate or a mixture of two or more of them. US 10224540 B2 describes _Al2O3 thin film coatings on porous silicon anodes using the ALD _method . US 10177365 B2 describes _AlWxFy or _AlWxFyCz thin film coatings on cathode _active materials comprising _LiCoO2 using _{ALD .} US 9531004 B2 describes a hybrid thin film coating on a group of anode materials using the ALD method, the coating comprising the first of _Al2O3 , _TiO2 , _{SnO2 , V2O5} , _HfO2 , _{ZrO2 ,} ZnO layer and a second layer of a fluoride-based coating, a carbide-based coating, and a nitride-based coating, the group of anode materials consists of: Lithium titanate Li(4 + x)Ti5O12, where 0

x

3 (LTO), graphite, silicon, silicon-containing alloys, tin-containing alloys, and combinations thereof.

The present invention provides a solution to deposit a metal oxide layer on the cathode or cathode active material by ALD or CVD, forming an artificial interface on the electrode to protect the electrode from rapidly degrading electrochemical behavior. These metal oxide layers reduce excessive decomposition of the electrolyte at the electrode/electrolyte interface during SEI formation, reducing capacity loss in the first few cycles. The presence of such a metal oxide layer also reduces the dissolution of the transition metal cations of the cathode active material caused by parasitic reactions between the electrolyte and the cathode active material, thereby reducing their redeposition on the anode. This increases the electrochemical activity of the battery. As discussed above, _other types of membranes have been proposed, especially pure metal oxides such as _Al2O3 . However, this type of material behaves as an ionic insulator and thus does not allow for optimal electrochemical performance of the resulting cathode and battery.

The present invention may be further understood by reference to the following non-limiting, exemplary embodiments described as enumerated sentences: 1. A method of coating a cathode or cathode active material with a metal oxide film, the method comprising the steps of: a1. The cathode or cathode active material is exposed to a chemical precursor vapor comprising a chemical precursor of the formula M(=NR ^a )(OR ^b ) ₂ (NR ^c ₂ ) and a source of oxygen as an oxidizing co-reactant, wherein: M is selected from From Nb, Ta or V, Ra is selected from iPr, tBu, t-Am Rb is each independently selected from Et, iPr, tBu, sBu, SPen, and Rc is each independently selected from Et or Me; and b1. metal oxidation A film of the object is deposited onto the cathode or cathode active material. 2. The method of statement 1, wherein the step a1. of exposing the cathode or cathode active material to a chemical precursor vapor is performed sequentially with the step a2. of exposing the cathode or cathode active material to co-reactants . 3. The method of statement 2, further comprising the step a1i. of purging the chemical precursor vapor prior to the step a2. of exposing the cathode or cathode active material to co-reactants. 4. The method of statement 3, wherein the step b1. of depositing the metal oxide film onto the cathode or cathode active material comprises an atomic layer deposition step. 5. The method of statement 3, wherein the step b1. of depositing the metal oxide film onto the cathode or cathode active material comprises a chemical vapor deposition step. 6. The method of any one of statements 1-5, wherein the co-reactant is an oxygen source, such as O2, O3, H2O, H2O2, NO, NO2, N2O or NOx; an oxygen-containing silicon precursor containing Oxytin precursors, phosphates such as trimethylphosphate, diethylamidophosphate, or sulfate. 7. The method of any one of statements 1-6, wherein the precursor has the formula M(=NR ^a )(OR ^b ) ₂ (NMeEt). 8. The method of any one of statements 1-7, wherein at least one of R ^b is independently selected from sBu, SPen. 9. The method of any one of statements 1-7, wherein the precursor has the formula M(=NR ^a )(OR ^b ) ₂ (NMeEt), and wherein at least one of R ^b is independently selected from sBu, SPen. 10. The method of statement 8 or 9, wherein both R ^b are independently selected from sBu, SPen. 11. The method of any one of statements 1-10, wherein the metal oxide film resulting from step b1. has an average atomic composition of Nb _x O _y D _z , O is oxygen, and D is a or more of any other atom, and where x = 0.3-0.4, y = 0.4-0.65, and z = 0.01-0.1. 12. The method of any one of statements 1-11, wherein the temperature of the chemical precursor vapor and/or the cathode or cathode active material is from 100°C to 300°C, more preferably 125°C °C to 275°C, even more preferably 125°C to 175°C. 13. The method of any one of clauses 1-12, wherein the metal oxide film has an average thickness of 0.02 nm to 10 nm, preferably 0.1 nm to 5 nm, most preferably 0.2 nm to 2nm. 14. The method of any one of statements 1-13, wherein the cathode active material, or the cathode active material in the cathode, is selected from the group consisting of: a) layered oxides, such as Ni-rich cathode materials like NMC (lithium nickel manganese cobalt oxide) and NCA (lithium nickel cobalt aluminum oxide); b) spinel cathode materials like LMO (lithium manganese oxide), LNMO (lithium nickel manganese oxide); c) Cathode materials of olivine structure, especially the olivine phosphate family, such as LCP (lithium cobalt phosphate), LFP (lithium iron phosphate), LNP (lithium nickel phosphate); and combinations thereof. 15. The method of any one of clauses 1-14, wherein one or more of steps a1. and b1. are performed from one to ten times, preferably one to three times, more preferably only once. 16. The method of any one of statements 1-15, wherein a) the temperature of the chemical precursor vapor and/or the cathode or cathode active material is from 100°C to 300°C, more preferably is 125°C to 275°C; b) the metal oxide film has an average thickness of 0.02 nm to 10 nm, preferably 0.1 nm to 5 nm, most preferably 0.2 to 2 nm; and c) The metal oxide film is at least 50% continuous, preferably 95% or more continuous, more preferably 98% or more continuous on the cathode or cathode active material surface.

The present disclosure provides a solution for forming an interface on an electrode to protect it from rapidly degrading electrochemical behavior. The electrode interface is formed on the cathode active material either before or after its incorporation into the final cathode. The metal oxide layer is formed by chemical vapor deposition (CVD) or atomic layer deposition (ALD) using a volatile chemical precursor M(=NR ^a )(OR ^b ) ₂ (NR ^c ₂ ), wherein: M is selected from Nb, Ta or V, R ^a is selected from iPr, tBu, t-Am, R ^b is each independently selected from Et, iPr, tBu, sBu, SPen, and R ^c is each independently selected from Et or Me.

The volatile chemical precursors are supplied simultaneously, sequentially and/or by pulses of the precursor gas phase. The method takes advantage of the unexpected efficiency of this genus to achieve improved cathode performance after less than nine ALD deposition cycles, preferably three or fewer cycles. This relatively small number of required ALD cycles significantly reduces the consumption of metals such as Nb or Ta and the time required to process the cathode or cathode active material.

"Metal oxide" and "metal oxide film" as used herein mean a transition metal oxide film with one or more additional elements such that the atomic ratio is MxOyDz, where M = aggregated moiety of one or more transition metals, O is oxygen, and D is an aggregation moiety of other elements such as aluminum, zinc, tin, carbon, lithium, and phosphorus. Typically, x ranges from 10% to 60%, y ranges from 10% to 60%, and z ranges from undetectable to 10%, preferably from 0 to 5%.

Preferably, M is a transition metal that forms one or more stable ions with incompletely filled d orbitals. In particular, M is Nb, but may further contain one or more of Ti, Zr, Hf, V, Ta, Cr, Mo or W as needed.

The metal oxide film is formed by CVD or ALD methods to deposit a metal oxide layer on the cathode active material before, during an intermediate step of manufacturing the final cathode, or after the cathode active material is bonded to the final cathode. The metal oxide film may be a continuous film that is fully coated with the cathode active material, such as by powder ALD on the powder cathode active material prior to inclusion in the cathode. The film can be discontinuous, either by controlled deposition conditions to limit film growth, or by incorporating the cathode active material into the cathode such that only a portion of its surface is exposed to the CVD or ALD deposition process. Generally, the metal oxide film has an average thickness of 0.125 to 10 nm, such as 0.125 nm to 1.25 nm, preferably 0.3 nm to 4 nm.

Metal oxide deposits can be deposited on electrodes, such as those consisting of: ● Layered structure oxides, preferably "NMC" (lithium nickel manganese cobalt oxide, such as NMC811 (Ni : Mn : Co = 8 : 1 : 1), and even NMC955 (Ni : Mn : Co = 9 : 0.5 : 0.5)), NCA (lithium nickel cobalt aluminum oxide) or LNO (lithium nickel oxide); ● Spinel, preferably LNMO (lithium nickel manganese oxide) or LMO (lithium manganese oxide); ● olivine (lithium-metal phosphate, where the metal can be iron, cobalt, manganese); ● Carbon anode forms such as graphite, doped or undoped; ● silicon anode, ● Silicon-carbon anode ● tin anode, ● silicon-tin anode, or ● Lithium metal.

Deposition can be on electrode active material powders, electrode active material porous materials, different shapes of electrode active materials, or on pre-formed electrodes (where the electrode active material may have been associated with conductive carbon and/or binders and may have been collected Fluid foil support).

" Cathode " in a Lithium-ion battery refers to the positive electrode in an electrochemical cell (battery) where, during charging, the cathode material is reduced by intercalation of electrons and lithium ions. During discharge, the cathode material is oxidized by releasing electrons and lithium ions. Lithium ions move within the electrochemical cell through the electrolyte from the cathode to the anode and vice versa, while electrons migrate through the external circuit. The positive electrode is usually composed of positive active materials (ie, lithiated metal layered oxides), conductive carbon black agents (acetylene black Super C65, Super P), and binders (PVDF, CMC) .

" Cathode active material " is the main element in the composition of the cathode (positive electrode) of a battery cell. The cathode material is, for example, cobalt, nickel and manganese in a crystal structure such as a layered structure forming a multimetal oxide material in which lithium is intercalated. Examples of cathode active materials are layered lithium nickel manganese cobalt oxide (LiNixMnyCozO2), spinel lithium manganese oxide (LMn2O4) and olivine lithium iron phosphate (LiFePO4).

" Continuity " with respect to a coating on a surface means that the surface has the percentage of coating material of any thickness. Continuity is typically assessed optically by imaging the coated material and quantifying the proposition (eg in ^nm2 ) whether the surface is covered by a film, eg by grid mapping the surface. Electron microscopy can be used to image the surface. The amount of coverage can be expressed as a percentage of the surface area of the substrate. Pinholes, gaps or other discontinuities in the film would mean less than 100% continuity.

Metal oxide films are formed by CVD or ALD methods using volatile chemical precursors of the species M(=NR ^a )(OR ^b ) ₂ (NR ^c ₂ ) and optionally one or more other chemistries that contribute to the final film formation. Precursor vapor formation. Any one or more additional suitable precursors may be selected for use based on their known suitability for forming metal oxides for other applications.

Under optimized deposition conditions, a wide range of optional precursors are suitable for use with Nau2 to form metal oxides.

Preferred Group IVA metal precursors are: ● M(OR) ₄ , where each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably M(OMe) ₄ , M( OiPr) ₄ , M(OtBu) ₄ , M(OsBu) ₄ ● M(NR ¹ R ² ) ₄ , wherein each R ¹ and R ² is independently a C1-C6 carbon chain (straight or branched chain), most Preferred are M(NMe ₂ ) ₄ , M(NMeEt) ₄ , M(NEt ₂ ) ₄ ● ML(NR ¹ R ² ) ₃ , where L represents unsubstituted or substituted allyl, cyclopentadiene Base, pentadienyl, hexadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, and each R ¹ and R ² are independently C1-C6 carbon chains (straight chain or branched chain), most preferably MCp(NMe ₂ ) ₃ , M(MeCp)(NMe ₂ ) ₃ , M(EtCp)(NEt ₂ ) ₃ , MCp*(NMe ₂ ) ₃ , MCp(NMe ₂ ) ₃ , M(MeCp)(NMe ₂ ) ₃ , M(EtCp)(NEt ₂ ) ₃ , MCp*(NMe ₂ ) ₃ , M(iPrCp)(NMe ₂ ) ₃ , M(sBuCp)(NMe ₂ ) ₃ , M (tBuCp)(NMe ₂ ) ₃ , N(secPenCp)(NMe ₂ ) ₃ , M(nPrCp)(NMe ₂ ) ₃ ● ML(OR) ₃ , where L represents unsubstituted or substituted allyl, cyclopentyl Dienyl, pentadienyl, hexadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, and each R is independently a C1-C6 carbon chain (straight or branched chain ), the most preferred are MCp(OiPr) ₃ , M(MeCp)(OiPr) ₃ , M(EtCp)(OEt) ₃ , MCp*(OEt) ₃ , M(iPrCp)(NMe ₂ ) ₃ , M( sBuCp)(NMe ₂ ) ₃ , M(tBuCp)(NMe ₂ ) ₃ , N(secPenCp)(NMe,) ₃ , M(nPrCp)(NMe ₂ ) ₃

Preferred VA group metal precursors are: ● M(OR) ₅ , where each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably M(OEt)5, M( OiPr)5, M(OtBu)5, M(OsBu)5 ● M(NR ¹ R ² ) ₅ , wherein each R ¹ and R ² is independently a C1-C6 carbon chain (straight or branched chain), most Preferred are M(NMe ₂ ) ₅ , M(NMeEt) ₅ , M(NEt ₂ ) ₅ ● ML(NR ¹ R ² ) _x , where x = 3 or 4, and L represents unsubstituted or substituted allyl base, cyclopentadienyl, pentadienyl, hexadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, or imide in the form of NR, and each ^R and R ² is independently a C1-C6 carbon chain (straight chain or branched chain), most preferably MCp(NMe ₂ ) ₃ , M(MeCp)(NMe ₂ ) ₃ , M(EtCp)(NEt ₂ ) ₃ , MCp*(NMe ₂ ) ₃ , M(=NtBu)(NMe ₂ ) ₃ , M(=NtAm)(NMe ₂ ) ₃ , M(=NtBu)(NEt ₂ ) ₃ , M(=NtBu)(NEtMe) ₃ , M(=NiPr)(NEtMe) ₃ . ● M(=NR ¹ )L(NR ² R ³ ) _x , where x = 1 or 2, L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl, hexadienyl , cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, and each R ¹ and R ² and R ³ are independently C1-C6 carbon chains, most preferably MCp(=NtBu)( NMe ₂ ) ₂ , M(MeCp)(N=tBu)(NMe ₂ ) ₂ , M(EtCp)(N=tBu)(NMe ₂ ) ₂ , MCp*(=NtBu)(NMe ₂ ) ₂ , MCp(= NtBu)(NEtMe) ₂ , M(MeCp)(N=tBu)(NEtMe) ₂ , M(EtCp)(N=tBu)(NEtMe) ₂ . ● ML(OR) _x , where x = 3 or 4, L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl, hexadienyl, cyclohexadienyl, cycloheptadienyl Dienyl, cyclooctadienyl, or imide in the form of NR, wherein each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably MCp(OiPr) ₃ , M (MeCp)(OiPr) ₃ , M(EtCp)(OEt) ₃ , MCp*(OEt) ₃ M(=NtBu)(OiPr) ₃ , M(=NtAm)(OiPr) ₃ , ● ML(OR) _x ( NR ¹ R ² ) _y , wherein x and y are independently equal to 1 or 2, and L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl, hexadienyl, cyclohexadiene group, cycloheptadienyl, cyclooctadienyl, or imide in the form of NR, wherein each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably MCp (OiPr ) ₂ (NMe ₂ ), M(MeCp)(OiPr) ₂ (NMe ₂ ), M(EtCp)(OEt) ₂ (NMe ₂ ), M(=NtBu)(OiPr) ₂ (NMe ₂ ), M(= NtBu)(OiPr)(NMe ₂ ) ₂ , M(=NtBu)(OiPr) ₂ (NMe ₂ ), M(=NtBu)(OiPr) ₂ (NEtMe), M(=NtBu)(OiPr) ₂ (NEt ₂ ), M(=NtBu)(OEt) ₂ (NMe ₂ ), M(=NtBu)(OEt) ₂ (NEtMe), M(=NtBu)(OEt) ₂ (NEt ₂ ), M(=NiPr)(OiPr ) ₂ (NMe ₂ ), M(=NiPr)(OiPr) ₂ (NMe ₂ ) ₂ , M(=NiPr)(OiPr) ₂ (NEtMe), M(=NiPr)(OiPr) ₂ (NEt ₂ ), M (=NiPr)(OEt) ₂ (NMe ₂ ), M(=NiPr)(OEt) ₂ (NEtMe), or M(=NiPr)(OEt) ₂ (NEt ₂ ).

Preferred VIA group metal precursors are: ● M(OR) ₆ , where each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably M(OEt)5, M( OiPr)5, M(OtBu)5, M(OsBu)5 M(NR ¹ R ² ) ₆ , wherein each R ¹ and R ² is independently a C1-C6 carbon chain (straight or branched chain), most Preferred are M(NMe ₂ ) ₆ , M(NMeEt) ₆ , M(NEt ₂ ) ₆ ● M(NR ¹ R ² ) _x L _y , wherein x and y are independently equal to 1 to 4, and L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl, hexadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, or imides in the form of NR, And each R ¹ and R ² is independently a C1-C6 carbon chain (straight chain or branched chain), most preferably MCp(NMe ₂ ) ₃ , M(MeCp)(NMe ₂ ) ₃ , M(EtCp) (NEt ₂ ) ₃ , MCp*(NMe ₂ ) ₃ , M(=NtBu) ₂ (NMe ₂ ) ₂ , M(=NtAm) ₂ (NMe ₂ ) ₂ , M(=NtBu)(NEt ₂ ) ₂ ● M (OR) _x (NR ¹ R ² ) _y L _z ML, where x, y and z are independently equal to 0 to 4, and L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl , hexadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, or imides in the form of NR, wherein each R is independently a C1-C6 carbon chain (straight or branched chain ), the most preferred are MCp(OiPr) ₃ , M(MeCp)(OiPr) ₃ , M(EtCp)(OEt) ₃ , M(=NtBu) ₂ (OiPr) ₂ , M(=NtAm) ₂ (OiPr ) ₂ , M(=NtBu) ₂ (OtBu) ₂ , M(=NiPr) ₂ (OtBu) ₂ , M(=NtBu) ₂ (OiPr) ₂ , M(=NiPr) ₂ (OiPr) ₂ . ● M(=O)xLy, where x, y and z are independently equal to 0 to 4, and L represents unsubstituted or substituted allyl, cyclopentadienyl, pentadienyl, hexadienyl, cyclo Hexadienyl, cycloheptadienyl, cyclooctadienyl, amide or imide in the form of NR, wherein each R is independently a C1-C6 carbon chain (straight or branched chain), most preferably M(=O) ₂ (OtBu) ₂ , M(=O) ₂ (OiPr) ₂ , M(=O) ₂ (OsecBu) ₂ , M(=O) ₂ (OsecPen) ₂ , M(=O ) ₂ (NMe ₂ ) ₂ , M(=O) ₂ (NEt ₂ ) ₂ , M(=O) ₂ (NiPr ₂ ) ₂ , M(=O) ₂ (NnPr ₂ ) ₂ , M(=O) ₂ (NEtMe) ₂ , M(=O) ₂ (NPen ₂ ) ₂ .

Metal oxide films can be formed using a member of the genus of volatile chemical precursors as a single precursor or in combination with one or more other precursors, in either case, optionally with an oxidizing co-reactant (if needed or desired) combination to form. Those skilled in the art are able to select suitable one or more additional precursors and co-reactants from those known in the art to produce a metal oxide film of the desired composition when used under optimized deposition conditions, Thus "tuning" the composition of the metal oxide. Exemplary guidance for various precursor options include: Oxygen can come from an O source such as _O2 , _O3 , _H2O , _{H2O2 ,} NO, NO2, N2O, or NOx Oxygen can come from a dopant source, Such as oxygen-containing silicon precursors, oxygen-containing tin precursors, phosphates such as trimethylphosphate, diethylamidophosphate, or sulfate. ● Nitrogen can come from N sources such as N ₂ , NH ₃ , N ₂ H ₄ , mixtures containing N ₂ H4 , alkylhydrazines, NO, NO2, N2O, or NOx ● Nitrogen can come from dopant sources such as nitrogen-containing Silicon precursors, nitrogen-containing tin precursors, or phosphates such as diethyl phosphoamidate. ● Carbon can come from C sources, such as hydrocarbons, carbon-silicon precursors, carbon-tin precursors, carbon-boron precursors, carbon-aluminum precursors, carbon-phosphorus precursors, phosphates such as trimethylphosphate, amines diethyl phosphate, or sulfate ester. ● Silicon can come from Si sources such as silanes or silicon-containing organometallic precursors. ● Tin can come from Sn sources such as stannanes or tin-containing organometallic precursors. ● Aluminum can come from Al sources such as alanes (including alkylalanes) or aluminum-containing organometallic precursors. • Phosphorus can be derived from phosphines, including organic phosphines, or phosphates such as trimethylphosphate or diethylamidophosphate. ● Sulfur can come from S sources, such as sulfur, S8, H2S, H2S2, SO2, organic sulfites, sulfates, or sulfur-containing organometallic precursors. ● The first row of transition metals can be derived from known organometallic compounds or other precursors suitable for vapor deposition. Examples Examples 1-5 : Deposition and electrochemical properties of NbO thin films deposited on NMC622 powder using Nau2/ _H2O at 250°C Experimental conditions for deposition / film formation:

The number of cycles on NMC622 electrodes or NMC powders is typically limited to 20 ALD cycles, corresponding to about 1.5 to 4 Angstroms, insufficient thickness for film synthesis. Therefore, such characterizations were performed on films deposited with _O3 after 300 ALD cycles on blank silicon wafers. By X-ray photoelectron spectroscopy (XPS), the corresponding growth rate and film composition are: ● GPC about 2.96 Å. Nb: about 38.7%, O: about 54.8%, C: about 3%, N: about 2%, Si about 1.4% ● The refractive index of these films is 2.38.

Deposition was performed on NMC622 powder using a fluidized bed reactor under the following experimental conditions: ALD Conditions for ALD Reactor set temperature 250°C Reactor pressure About 40 Torr Number of Cycles 1/2/3/9 cycles Precursors and Gases Nautilus2 small tank temperature 100°C Nautilus2 small tank pressure 50 torr N2 bubbling 20 sccm in Nautilus2 O3 FR 20 sccm N2 push/purge Approx. 120 sccm pulse sequence Nautilus2 (2 sccm) 900 seconds Purge 1040 seconds H2O 180 seconds Purge 1040 seconds load substrate 5 g of NMC622 powder

The chemical precursor in these examples is Nb(=NtBu)(NEt ₂ )(O− tBu ) ₂ (“Nau2”). Electrochemical Characterization: Experimental Conditions: Cell Conditions: • Cathode Material: NMC622 o About 5 mg/cm ² Loading o No Calendering • Coating Material: Nb ₂ O ₅ o Precursor: Nautilus2 o Co-Reactant: O ₃ or H ₂ O o Deposition T = 250°C o Powder reactor P < 40 Torr o Amount of powder coated: 5 g o Reactor filling: x% Membrane: Celgate 2400 Pure electrolyte: 1 M LiPF ₆ in EC : In EMC (1 : 1 wt) • Anode material: Li metal Measuring conditions: • Temperature: 26°C • 3 pre-cycles at 0.2C, then at 1C • Voltage: 3.0-4.3 V, CC

As seen in Figure 1, the amount of niobium deposited as niobium oxide increased from one ALD cycle to 2-3 ALD cycles, and increased significantly in the case of nine ALD cycles. The effect of these niobium oxide deposits is shown in Figures 2 and 3 . The battery performance was significantly enhanced compared to the uncoated control. However, very unexpectedly, a single ALD cycle produced the best results, but 2-3 cycles were close. 9 ALD cycles also did improve performance compared to the control, but not as much as 1-3 cycles. Typically, ALD coating of cathode active materials requires 5-20 ALD cycles for optimal benefit. Nau2 surprisingly achieves fewer ALD cycle processes that require much less time and a much lower precursor mass per unit of cathode active material. This would yield significant cost savings in industrial use.

ALD was performed using the same conditions and tests using ozone instead of water. The results for ozone were the same as for water, indicating that low cycle deposition was largely unaffected by the oxidant used.

Similar TGA and DTA properties were measured for the Ta analog Ta(=NtBu)(NEt ₂ )(O- tBu ) ₂ . Deposition with ₀₃ on silicon wafers for 200 cycles also produced similar results as seen for Nb(=NtBu)( _NEt2 )(O- tBu ) ₂ . At 275°C, the growth rate was 4.69 Å/cycle, and the composition was Ta: 32.8%, O: 56.5%, and C: 8.1%. Based on these results, it is expected that 1-9 ALD cycles for the cathode or cathode material coating will yield similar benefits in electrode performance as demonstrated above for Nau2.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in view of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. The invention may suitably comprise, consist of, or consist essentially of the disclosed elements, and may be practiced in the absence of non-disclosed elements. Also, language referring to order, such as first and second, if present, should be understood in an exemplary sense, not a limiting sense. For example, those skilled in the art will recognize that certain steps may be combined into a single step.

The singular forms "a/an" and "the" include plural referents unless the context clearly dictates otherwise.

"comprising" in the claims is an open transitional term that refers to a non-exclusive list of subsequently determined claim elements, i.e., anything else may be additionally included and kept within the scope of "comprising/ Include" range. "Comprising" is defined herein to necessarily cover the more restrictive transitional terms "consisting essentially of" and "consisting of"; thus "comprising/comprising" may be replaced by "consisting essentially of" or "Consisting of" replaces and remains within the expressly defined scope of "comprising/comprising".

"Provide" in the claims is defined to mean furnishing, supplying, making available or preparing something. This step may conversely be performed by any actor in the absence of explicit language in the claim.

Optional or optional means that the subsequently described event or circumstance may or may not occur. The specification includes instances where the event or circumstance occurs and instances where the event or circumstance does not occur.

Ranges can be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is understood that another embodiment is from the one particular value and/or to the other particular value, as well as all combinations within the stated range.

All references identified herein are each hereby incorporated by reference into this application in their entirety; likewise for specific information for each reference.

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In order to further understand the nature and purpose of the present invention, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which similar elements are given the same or similar reference numerals, and in the accompanying drawings: [Fig. 1] shows Photoelectron spectroscopy results of NbO film deposition on NMC622 powder using Nb(=NtBu)(NEt ₂ )(O- t Bu) ₂ (“Nau2”)/H ₂ O using a powder ALD (PALD) reactor; [ Figure 2] Shows the normalized C-rates of NbO thin films deposited on NMC622 powder using Nb(=NtBu)( _NEt2 )(O- tBu ) ₂ / _H2O in a powder ALD (PALD) reactor performance (normalized to their original discharge capacity at 2C); [Fig. 3] shows the use of Nb(=NtBu)(NEt ₂ )(O- t Bu) ₂ / Long-term cycling performance of NbO thin films deposited by _H2O on NMC622 powder; and [Fig. micrograph. The layer is identified by an arrow, part of which is also enclosed by a horizontal bar. The layer was visually confirmed to be continuous and conformal, with a thickness of approximately 1.5 nm-2 nm. The conformal coverage and Nb content of this layer was further confirmed by energy dispersive X-ray spectroscopy (not shown).

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Claims (17)

A method of coating a cathode or cathode active material with a metal oxide film, the method comprising the steps of: a1. exposing the cathode or cathode active material to a compound having the formula M(=NR ^a )(OR ^b ) ₂ (NR ^c ₂ ) a precursor chemical precursor vapor and an oxygen source as an oxidizing co-reactant, and b1. depositing a metal oxide film onto the cathode or cathode active material, wherein: M is selected from Nb, Ta or V, R ^a is selected from iPr, tBu, t-Am, R ^b is each independently selected from Et, iPr, tBu, sBu, SPen, and R ^c is each independently selected from Et or Me. The method as claimed in claim 1, wherein the precursor has the formula M(=NR ^a )(OR ^b ) ₂ (NMeEt). The method according to claim 1, wherein at least one of R ^b is independently selected from sBu and SPen. The method of claim 1, wherein the precursor has the formula M(=NR ^a )(OR ^b ) ₂ (NMeEt), and wherein at least one of R ^b is independently selected from sBu, SPen. The method according to claim 3 or 4, wherein both R ^b are independently selected from sBu and SPen. The method as described in Claim 1, wherein the precursors are Nb(=NtBu)(NEt ₂ )(O- t Bu) ₂ , Nb(=NtBu)(NEt ₂ ) ₂ (O- t Bu), Ta (=NtBu)(NEt ₂ )(O- t Bu) ₂ , Ta(=NtBu)(NEt ₂ ) ₂ (O- t Bu), and mixtures thereof. The method of claim 1, wherein the step a1. of exposing the cathode or cathode active material to chemical precursor vapor is performed sequentially with the step a2. of exposing the cathode or cathode active material to co-reactants. The method of claim 2, further comprising the step a1i. of purging the chemical precursor vapor prior to the step a2. of exposing the cathode or cathode active material to co-reactants. The method of claim 3, wherein the step b1 of depositing the metal oxide film onto the cathode or cathode active material comprises an atomic layer deposition step. The method as claimed in claim 3, wherein the step bl. of depositing the metal oxide film onto the cathode or cathode active material comprises a chemical vapor deposition step. The method as described in any one of claims 1-5, wherein the co-reactant is an oxygen source, such as O2, O3, H2O, H2O2, NO, NO2, N2O or NOx; oxygen-containing silicon precursors, oxygen-containing Tin precursors, phosphates such as trimethylphosphate, diethylphosphonoamidate, or sulfates. The method according to any one of claims 1-11, wherein the metal oxide film produced by step b1. has an average atomic composition of Nb _x O _y D _z , O is oxygen, and D is one or Multiples of any other atom, and where x = 0.3-0.4, y = 0.4-0.65, and z = 0.01-0.1. The method according to any one of claims 1-12, wherein the temperature of the chemical precursor vapor and/or the cathode or cathode active material is from 100°C to 300°C, more preferably 125°C C to 275°C, even more preferably 125°C to 175°C. The method according to any one of claims 1-13, wherein the metal oxide film has an average thickness of 0.02 nm to 10 nm, preferably 0.1 nm to 5 nm, and most preferably 0.2 to 5 nm. 2 nm. The method according to any one of claims 1-14, wherein the cathode active material, or the cathode active material in the cathode, is selected from the group consisting of: a) layered oxides, such as Ni-rich Cathode materials like NMC (Lithium Nickel Manganese Cobalt Oxide) and NCA (Lithium Nickel Cobalt Aluminum Oxide); b) spinel cathode materials like LMO (Lithium Manganese Oxide), LNMO (Lithium Nickel Manganese Oxide); c ) Cathode materials of olivine structure, especially the olivine phosphate family, such as LCP (lithium cobalt phosphate), LNP (lithium nickel phosphate), LFP (lithium iron phosphate); and combinations thereof. The method according to any one of claims 1-15, wherein one or more of steps a1. and b1. are performed from one to ten times, preferably one to three times. The method as claimed in claim 16, wherein a) the temperature of the chemical precursor vapor and/or the cathode or cathode active material is from 100°C to 300°C, more preferably 125°C to 175°C C; b) the metal oxide film has an average thickness of 0.02 nm to 10 nm, preferably 0.1 nm to 5 nm, most preferably 0.2 to 2 nm; and c) the metal oxide film is in the The cathode or cathode active material is superficially at least 50% continuous, preferably 95% or more continuous, more preferably 98% or more continuous.

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